


Thinking Fast and Slow

by Ilye



Category: Captain America (Movies), Marvel Cinematic Universe
Genre: Apologies to Daniel Kahneman, M/M, Mind Control Aftermath & Recovery, Neurology & Neuroscience, Not Captain America: Civil War (Movie) Compliant, Post-Captain America: The Winter Soldier, Post-Recovery Bucky Barnes, Post-Traumatic Stress Disorder - PTSD
Language: English
Status: Completed
Published: 2016-06-12
Updated: 2016-06-12
Packaged: 2018-07-14 17:22:40
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,666
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7183133
Author URL: https://archiveofourown.org/users/Ilye/pseuds/Ilye
Summary: <blockquote class="userstuff">
              <p>
  <i>Barnes isn’t used to engaging his System Two, Banner reckons. System Two is thinking slow. It’s rational, thoughtful and overrides the instincts. Barnes laughed at that. Of course he’s not used to engaging his System Two. Every time he tried he got electrocuted in the head. </i>
</p>
            </blockquote>





	Thinking Fast and Slow

**Author's Note:**

> First venture into a fandom larger than 100 people. Slightly overwhelmed; please be gentle. (It’s mildly irksome that it only took me three weeks of headlong descent into the Stucky archives and a behavioural neuroscience conference at work to write this.) Comments and feedback are more than welcome :)
> 
> Apologies to Daniel Kahneman, from whom I [stole the title](http://www.goodreads.com/book/show/11468377-thinking-fast-and-slow) and bastardised the [System One/Two theory](http://upfrontanalytics.com/market-research-system-1-vs-system-2-decision-making/).

See, the thing about Banner is that he's some huge brain in a normal-sized skull. Which is funny, when Barnes thinks about it, because he's also some huge green monster in a normal-sized body. But Banner also knows a few things about how the brain works, and a few other things about controlling his own (or not), which is how come he and Barnes are slugging it through Kahneman’s theories on thought.

Take Barnes’ swearing. The thing about being told that he cusses like a docker is that it's true. He was a docker, once – that's what the books say. That's what Steve says (so it shouldn’t be a surprise to him when Barnes creates the next novel way of taking the Lord’s name in vain, but it still earns him the judgey eyebrows. Barnes hates the judgey eyebrows.) And it must be one of those things that's got stuck in the neural circuitry and repeats itself at random.

The swearing, that is.

There are a lot of other things that also got stuck in the neural circuitry and repeat themselves at random. Barnes wishes a few more of them originated in the Brooklyn docks.

According to Banner, it’s not actually that random anyways. It's Barnes’ System One that makes him react the way he does to things, Banner says. It’s Barnes thinking fast. It’s the System One that makes him startle and spin with his shiv already flicked out from Jesus-knows-where. That makes his empty trigger finger spasm when a security guard looks at him wrong. That make his arm-plates whirr when anyone gets too close behind him.

That makes him curl around Steve at night, back-to-chest and knees hooked together, sharing the body heat that neither of them needs because they both run like furnaces now and the future is climate-controlled.

Barnes isn’t used to engaging his System Two, Banner reckons. System Two is thinking slow. It’s rational, thoughtful and overrides the instincts. Barnes laughed at that. Of course he’s not used to engaging his System Two. Every time he tried he got electrocuted in the head.

Thinking fast versus thinking slow. He can make decisions when he engages System Two. He can override the automatic. The System One habits? They got there through practice, through repetitive thinking, through conditioning. Essentially, Banner’s teaching him how to put mind over monster and retrain his brain.

(It don’t matter what anyone says about overriding his programming on the helicarrier, about hauling Steve out of the Potomac. That, Barnes knows, was _all_ instinct and it ain’t one he’s about to start changing.)

He never knew the brain had two systems. Until very recently _his_ brain had no system at all, just a tangle of wires with the insulation missing so they short-circuited at random and woke him screaming in the night or got him pulling a pistol on someone or left him passed out on the floor.

Right. Not so random. But also, not so fun.

What he did just there? That was his System Two overriding his System One.

Under the right conditions, normal human nerves can regenerate their insulation. Or so Barnes has been told, anyway. Nobody’s ever cultured super-soldier neurons and lived to either tell the tale or propagate the files, but Stark’s extrapolated enough whilst he’s been elbow-deep in Barnes’ arm so who knows? Maybe the serum’s doing a half-decent job of winding insulation tape back around the rats’ nest that is Barnes’ grey matter.

(He mentioned that to Banner and kicked off a long spiel without analogy into the difference between grey matter and white matter and myelin, and Barnes tried to keep up, he really did, but in the end he was so damned bored that faking a seizure seemed like the only way to shut Banner up. It earned him the judgey eyebrows again when Steve found out, but when Banner’d cottoned on after Barnes started laughing from his spasms on the floor, he’d honest-to-God laughed himself and started talking about how great play behaviour is because it’s a high-risk activity and stimulates neuroplasticity, but is instantly switched off by fear and stress.

Everyone in Stark Tower is a high-risk activity. Even taking a piss in the place is a high-risk activity, what with the self-flushing johns that had given Barnes a full-on panic attack the first time he encountered one. By rights, being alone in a room with a sackful of PTSD and a potential hulk-monster should mean he needed to use those johns on a far more frequent basis than he did.

Barnes added redefining ‘high risk’ to his System Two recalibration list.)

But the problem, Banner says, the problem with System One is that it's easy to become blind to the details. Arriving at home without recollection of driving the familiar route is the example they use, but Barnes doesn't drive, not anymore. But it's the same as flipping a squeaky-clean Glock 37 into his hand without memory of how the rags on the table got so cruddy. It’s realising he’s beaten Barton to sitting pretty in the room’s best lookout, with no recollection of assessing the joint.

It's not knowing how you ended up in Steve's bed in the first place, that night or the night before or the night before that.

It doesn’t make it _okay_ that it all comes from conditioned neural habitats. But the thing with learning how his brain works is that it also helps Barnes figure out how it _doesn’t_. He’s fucked up, and how! But it was the same attitude towards a gun that made him into a world-class sniper.

Well, that and a few other things.

(Huh, brain-like-a-gun. He wonders how Banner will take to that analogy.)

Whatever. Destructive curiosity’s gotten him a long way. Barnes was always good with the logic and he’s learned a thing or two from maintaining the wires in his arm, so knowing that it’s possible to rehash the whole tangle in his head gives him the same optimistic feeling he gets when a pinless grenade rolls his way with a whole two seconds left on the clock. He just hopes that nobody has to go in there and solder the connections in his brain back together like in his arm.

(Banner didn’t mind the circuit-board analogy. He’d smiled around the eyes when Barnes said it, but Banner never had electricity applied to his prefrontal cortex before.)

Bucky’s explaining all this to Steve one evening, like his shrink told him to, like a good little boy, and he’s so bored of it himself that he can’t blame Steve when his eyes glaze over.

“Steve.” Barnes snaps his metal fingers in front of Steve’s face. They spark, which is kinda cool. “Yo, Steve!”

Steve’s eyes clear and his attention re-enters the atmosphere. “Sorry. What you said about the solder just reminded me of –” He paused, squinting at Barnes. “Hey, Buck, you know, you always call me by my name.”

Barnes stared. Jesus, Mary and Stalin, Steve’s stupid was definitely wired into his System One.

“Not ‘Rogers’, or ‘Cap’, or anything creative like you and Stark come up with for each other.”

“Stark’s a dumbass sonovabitch, just like his pa.”

Steve’s eyebrows intimate that he isn’t pleased by the language, but neither does he disagree. Barnes blinks at him, slowly and deliberately. See? System Two right there.

“Everyone else gets called by surname,” Steve goes on. “Or worse. Even yourself.”

Especially himself. Barnes makes a stupendous System Two effort to avoid darting into that neural labyrinth.

“What’s your point, pal?”

Steve shrugs and rubs the back of his neck. Barnes gets a sense of the stubble there bristling and his arm-plates stiffen to match the goosebumps on his flesh arm.

“Not sure I got one,” Steve admits. “I’m not the neuroscientist with the complex theories. I just wondered, y’know, if it had any significance.”

Barnes focuses on making his best withering glare. He doesn’t have to focus very hard. “Well ‘course it’s significant. It’s your _name_ , ain’t it? Pick a German shrink and call it by whatever theory you want, but I’ve always called you by your name. I got enough habits to unpick and as long as you’re still ‘Steve’ then I don’t see why I gotta bother with that one to boot.”

Steve’s smiling. It’s a good look on him. Barnes gets goosebumps again and shifts his antsy metal arm to lie along the back of the couch.

“Y’know,” he says, looking away from Steve because even a supersoldier can’t focus on that smile _and_ rewiring his brain at the same time, “we could keep working on other items on my list instead.”

Steve’s smile brightens by at least one hundred lux. “Need help doing your homework, huh?”

Barnes cocks his lip into a smirk and nods. His fingers whirr as they twitch against the couch. “You betcha, champ. Can’t get through it on my own.”

“Ah.” Steve slips from the couch’s arm to its seat with too much enthusiasm for grace. “What’s the subject tonight?”

“Same as last time,” Bucky purrs because Steve’s close enough to hear it now and _really_ , that tone was all instinct. “Listen to my instincts and rationalise them. Focus on what I want, take my time to explore – you know the drill.”

“Sure thing, pal.” Steve’s hands are on his thighs now. Focus: check. “Take it slow, yeah?”

“As molasses.” Barnes’ focus has narrowed to the face in front of him, all ritzy blue eyes and cheekbones and stubbled, squared-off chin. Rationalise instincts: check. This is the face he’s jerked off to since he hit puberty. This is the fella he wants.

He hitches one knee up and opens the other. Steve slots right in the gap and leans in, real slow.

Molasses in January. It takes fucking forever for their lips to meet.

(When they do, Barnes knows his Systems One _and_ Two will short-circuit and leave him high and dry. And he’s totally down with that.)


End file.
